A Study of Effects of Temperature and Medium on Reaction of Triethylamine with Ethyl Bromide

1994 ◽  
Vol 59 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
Taťjana Nevěčná ◽  
Vojtěch Bekárek ◽  
Oldřich Pytela
Keyword(s):  
Activation Enthalpy ◽  
Solvent Polarity ◽  
Correlation Equation ◽  
Ethyl Bromide ◽  
Activation Entropy ◽  
Thermodynamic Quantities ◽  
Isokinetic Relationship ◽  
Complex Evaluation ◽  
Effects Of Temperature ◽  
The Individual

The rate constants of reaction of triethylamine with ethyl bromide have been measured in 13 solvents at the temperatures of 293, 313, 333, and 373 K. The activation entropies in the individual solvents increase when going from nonpolar to dipolar aprotic and polar protic solvents, which is explained by dominant solvation of the basic triethylamine and by formation of highly ordered associates without solvent in the activated complex in nonpolar solvent media. No isokinetic relationship has been found between the activation entropy and activation enthalpy, which indicates different solvent effects on the two quantities. The activation enthalpy and entropy of the reaction investigated are close to those of the reaction of triethylamine with ethyl iodide. Three methods have been used to evaluate the effect of medium at all the temperatures, their success being decreased in the order: Pytela's method - Kamlet-Taft - Koppel-Palm. Irrespective of the temperature, all the methods indicate that the reaction is accelerated by the solvent polarity, the significance of other effects being reflected differently depending on the temperature and the correlation equation used. A complex evaluation involving also the interpretation of the entropy and enthalpy components by means of empiric solvent parameters has shown that the resulting Gibbs energy represents a superposition of different effects of solvents on the two thermodynamic quantities, the solvent effect upon the activation entropy being predominant at the higher temperatures.

Kinetic Studies on the Polymerization of Dicyclohexylmethylmethane-4,4'-Diisocyanate with Polyoxytetramethylene Diol

2013 ◽  
Vol 791-793 ◽  
pp. 32-35
Author(s):  
Jian Cheng Wang
Keyword(s):  
Rate Constant ◽  
Arrhenius Equation ◽  
Activation Enthalpy ◽  
Kinetic Studies ◽  
Activation Entropy ◽  
Dimethyl Acetamide ◽  
Different Temperatures ◽  
Ft Ir ◽  
Temperature Activation

Dicyclohexylmethylmethane-4,4'-diisocyanate is used to react with polyoxytetramethylene diol at different temperatures. N,N-Dimethyl acetamide is used as solvent.In situFT-IR is used to monitor the reaction to work out rate constant, Arrhenius equation and Eyring equation. The polymerization has been found to be a second order reaction, and the rate constant increases with the rise of temperature. Activation energy (Ea), activation enthalpy (ΔH) and activation entropy (ΔS) for the polymerization are respectively calculated out, which are very useful to reveal the reaction mechanism.

A new classification of solvents based on chemometric empirical scale of parameters

1990 ◽  
Vol 55 (3) ◽  
pp. 644-652 ◽  
Author(s):  
Oldřich Pytela
Keyword(s):  
Causal Relation ◽  
Carbon Disulphide ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Solvent Polarity ◽  
Clustering Methods ◽  
Hexamethylphosphoric Triamide ◽  
Centroid Method ◽  
The Individual

The paper presents a classification of 51 solvents based on clustering in three-dimensional space formed by the empirical scale of PAC, PBC, and PPC parameters designed for interpretation of solvent effect on a model with cross-terms. For the classification used are the clustering methods of the nearest neighbour, of the furthest neighbour, of average bond, and the centroid method. As a result, the solvents have been divided into 8 classes denoted as: I - nonpolar-inert solvents (aliphatic hydrocarbons), IIp - nonpolar-polarizable (aromatic hydrocarbons, tetrachloromethane, carbon disulphide), IIb - nonpolar-basic (ethers, triethylamine), IIIp - little polar-polarizable (aliphatic halogen derivatives, substituted benzenes with heteroatom-containing substituents), IIIb - little polar-basic (cyclic ethers, ketones, esters, pyridine), IVa - polar-aprotic (acetanhydride, dialkylamides, acetonitrile, nitromethane, dimethyl sulfoxide, sulfolane), IVp - polar-protic (alcohols, acetic acid), and V - exceptional solvents (water, formamide, glycol, hexamethylphosphoric triamide). The information content of the individual parameters used for the classification has been determined. The classification is based primarily on solvent polarity/acidity (PAC), less on polarity/basicity (PBC), and the least on polarity/polarizability (PPC). Causal relation between chemical structure of solvent and its effect on the process taking place therein has been established.

Significance test of refractive index of solvent in evaluation of effect of medium on rates of quaternization reactions of methyl iodide with amines

1990 ◽  
Vol 55 (1) ◽  
pp. 180-184 ◽  
Author(s):  
Taťjana Nevěčná ◽  
Vojtěch Bekárek
Keyword(s):  
Refractive Index ◽  
Methyl Iodide ◽  
Rate Constants ◽  
Relative Permittivity ◽  
Significant Contribution ◽  
Activation Enthalpy ◽  
Dipole Moments ◽  
Significance Test ◽  
Activation Entropy ◽  
Aprotic Solvents

The rate constants have been measured of the reactions of methyl iodide with triethylamine (I) and tributylamine (III) at 293 K in twelve aprotic solvents, methyl iodide with tripropylamine (II) at 293, 313, 323, and 333 K in fifteen solvents differing greatly in their dipole moments, relative permittivities, and refractive indexes, and diiodomethane with tripropylamine in diiodomethane at 293 K (k1 = 2.1 10-5 s-1). The aprotic solvents predominantly affect the activation entropy which for the reaction of II varies from -200 J mol-1 s-1 (in cyclohexane) to -108 J mol-1 s-1 (in diiodomethane). The activation enthalpy of the reaction of methyl iodide with tripropylamine (II) is only little affected by aprotic solvents, a significant increase in activation enthalpy has been observed in the case of amphiprotic solvents. The evaluation of effect of medium on the rate constants of the above-mentioned reactions by means of the Kirkwood functions of relative permittivity and refractive index has shown a significant contribution of the refractive index of solvent which is comparable with the effect of relative permittivity.

The Thermal Dependence of Flagellar Activity in Strigomonas Oncopelti

1965 ◽  
Vol 42 (3) ◽  
pp. 537-544
Author(s):  
M. E. J. HOLWILL ◽  
N. R. SILVESTER
Keyword(s):  
Activation Enthalpy ◽  
Beat Frequency ◽  
Published Data ◽  
Activation Entropy ◽  
Present Value ◽  
Kcal Mole ◽  
Thermal Dependence ◽  
Flagellar Beat ◽  
Rate Limiting

The flagellar beat frequency of Strigomonas oncopelti was found by cinémicrophotography at temperatures in the range 4-45° C. The thermal dependence is described by an activation enthalpy (ΔH‡) of 15.4 kcal./mole and an activation entropy (ΔS‡ of -1 e.u. ΔH‡ is comparable with published data on cilia and glycerol-extracted sperm. Values of ΔS‡ (-20 e.u.) deduced from the literature suggest a rate-limiting reaction between ions of like charge although the present value does not support this idea.

Kinetics of acid-catalyzed hydrolysis of fluorinated propanoates

1983 ◽  
Vol 48 (10) ◽  
pp. 2805-2811 ◽  
Author(s):  
Oldřich Paleta ◽  
Jaroslav Kvíčala ◽  
Václav Dědek
Keyword(s):  
Rate Constants ◽  
Relative Rate ◽  
Chloride Concentration ◽  
Activation Entropy ◽  
High Activation ◽  
Isokinetic Relationship ◽  
Relative Rate Constants ◽  
Acid Catalyzed ◽  
Kinetics Of ◽  
Hydrolysis Of

Rates of hydrolysis, kH+, of methyl 2-chloro-2,3,3,3-tetrafluoro-(III), 2,3-dichloro-2,3,3-trifluoro-(IV), 2,2,3-trichloro-3,3-difluoro-(V), 2,3,3,3-tetrafluoro-(VI) and 3-chloro-2,3,3-trifluoropropanoate (VII) were measured in 0.5M-HCl in aqueous methanol (80% vol; 76% wt) at 40, 50 and 60 °C. The relative rate constants, krel (50 °C), (for the propanoate III, kH+ = 4.3 . 10-5 l mol-1 s-1; krel = 100) are 311, 100, 38, 9.4, 44 and 15 for the esters II, III, IV, V, VI and VII, respectively (experimental error ±9%). It was found that krel = αβ where α and β are the following factors for groups in the position 2 and 3: CClF 10, CHF 4.2, CCl2 2.8, CF3 10 and CClF2 3.6. The rate constants obey the isokinetic relationship. For the ester III the dependence of log kobs on logarithm of hydrogen chloride concentration is linear at concentrations 0.08-2.4 mol l-1 which, together with high activation entropy ΔS≠ for the esters III-VII (-167 to -217 J mol-1 K-1), shows that the hydrolysis proceeds by an AAC2 mechanism.

EFFECTS OF TEMPERATURE ON CHANGES IN THE NITROGENOUS CONSTITUENTS OF MIXED FOREST LITTERS DURING DECOMPOSITION AFTER INOCULATION WITH VARIOUS MICROBIAL CULTURES

1974 ◽  
Vol 54 (4) ◽  
pp. 387-394 ◽  
Author(s):  
F. J. SOWDEN ◽  
K. C. IVARSON
Keyword(s):  
Amino Acid ◽  
Mixed Forest ◽  
Soil Extract ◽  
Total N ◽  
Intermediate Period ◽  
Microbial Cultures ◽  
Heated Milk ◽  
Treated Leaf ◽  
Effects Of Temperature ◽  
The Individual

A study was made of the effects of temperature and different microorganisms, or mixtures of microorganisms, on the changes in the nitrogenous constituents of mixed forest litters (mixed pine, oak, maple) during decomposition periods of up to 4 yr at 1, 4, 10, and 27 C. The percentage of total-N in the decomposing materials increased with time, the increase being related to loss in weight of sample. The percentage of amino-N/total-N was higher with the soil-extract-treated leaf mixture than with the fungi-inoculated material; it increased to a maximum at some intermediate period, then decreased, and was highest with the 930 day 27 C material. Most of the individual amino acids increased in amount up to 930 days; then decreased, the amounts being, in general, higher with higher temperatures. Much of this increase was related to loss in weight of sample, but there appeared to be some net synthesis of amino acid. Lysine and, to a lesser extent, histidine were exceptions to this generalization. The amounts of hexosamines increased with decomposition: with the soil-extract-treated materials the increase of galactosamine was relatively greater than that of glucosamine, but little or no galactosamine was found in any of the fungi-inoculated materials. The amino acid ratios, i.e., the proportion of one relative to another, did not change in any consistent fashion, except for lysine. With the fungi-inoculated material, autoclaving reduced the amount of lysine to less than one-half and a ninhydrin-reacting material appeared before arginine on the amino acid chromatograms; its amount was not changed during decomposition. It may be similar to lysine derivatives found in acid hydrolyzates of heated milk.

scholarly journals The Alkaline solvolysis of allyl bromide in alcohol-water solvents

2021 ◽  
Author(s):  
◽  
Valda Hilary Donald
Keyword(s):  
Nucleophilic Substitution ◽  
Rate Constant ◽  
Solvent Effects ◽  
Rate Constants ◽  
Allyl Bromide ◽  
Solvent Polarity ◽  
Specific Rate ◽  
Increase With Increase ◽  
Alcohol Water ◽  
The Individual

<p>The rate of the alkaline solvolysis of allyl bromide has been measured in various ethanol-water and methanol-water mixtures. This has been found to increase with increase in solvent polarity. An attempt was made to explain this behaviour in terms of partial ionisation of the substrate. It has been suggested that in nucleophilic substitution the individual specific rate constants for attack by alkoxide or hydroxide ions are a better indication of solvent effects than the apparent overall rate constant.</p>

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